An inscription in Bath Abbey to the memory of the castrato singer Venanzio Rauzzini. Photograph: Ian M Butterfield/Alamy

The following correction was printed in the Guardian's Corrections and clarifications column, Tuesday 13 April 2010

An editing change had us saying that Michael Maniaci and Radu Marian are both to sing at Bath Abbey on Thursday. This applies to the latter only

His gravestone is barely noticeable on the floor of Bath Abbey, walked over and ignored by thousands each week, while a commemorative plaque is hidden in a corner behind hymn book trolleys. Yet the man was one of the most talented – but scandalised – singers of his generation: a musical superstar as well known for bedhopping as he was for the thrilling beauty of his voice.

On Thursday the astonishing life of the castrato Venanzio Rauzzini will be celebrated at Bath Abbey, the venue – 200 years to the day – of his funeral in 1810.

"He was a truly remarkable man, the Pavarotti of his day," said Jason Thornton, artistic director of the Bath Philharmonia and the man behind the concert. "And it was because of him that Bath is the festival city that it is."

But in celebrating the life of Rauzzini, organisers have also come across a mystery: was he or wasn't he?

The conventional wisdom is that Rauzzini was one of those unfortunate boys castrated or snipped on the orders of choirmasters in an age when the castrati were the most revered and celebrated of singers.

But in his programme notes for the concert, local Rauzzini expert Raimund Herincx, a retired opera singer, suggests that Rauzzini could not have been castrated and that his unnatural voice was entirely natural.

Rauzzini was born in 1746 in Camerino, a small town near Rome, and became a star of the Sistine choir. His singing talent was breathtaking. It electrified audiences and he became known throughout the continent.

He was also a ladies' man, a kind of castrato Casanova, sleeping his way round Europe with rich men's wives who assumed the sex was risk-free.

"He seems to have been doing everybody all round Europe, being chased from one city to another," said Thornton.

Herincx has come across hearsay evidence that suggests that Rauzzini had a secret. Addressing the question of why, aged 27, Rauzzini ended up in England, he writes: "There were rumours which persisted throughout his life which may well have caused Rauzzini to leave the continent. These have encouraged me to believe that he was not a castrato, but a natural male soprano."

One obituary, in the Gentleman's Magazine, alludes to this, saying: "His principal embarrassments were occasioned early in life by the advantages that were taken of his inexperience and facility."

What is definitely known is that he was hounded out of cities including Munich, Frankfurt, Dublin and London before arriving in Bath, then something of a party city.

"We think one reason he ended up in Bath is that he wasn't in fact safe sex," said Thornton. "In Bath, of course, people didn't mind scandal so much, you could live through it."

Fascinating though it is, Thornton hopes Rauzzini will be remembered for much more than his philandering.

He was also extraordinarily talented, and able as a boy, it is said, to sight-read difficult music upside down. A young Mozart wrote music with Rauzzini in mind, including the leading male role in his opera Lucio Cilla and the famous motet Exultate Jubilate.

Rauzzini was hugely in demand and became extraordinarily rich.

After retiring from the stage and settling in Bath – spending his money on large swaths of property – he became the most sought-after singing teacher in Britain as well as being a generous benefactor, financing the subscription concert series. Bath, because of Rauzzini, began to overtake London in terms of musical standards.

Rauzzini would have been known by all the composers of his day but he was a particular friend of Haydn, who came to stay with the singer for six weeks in 1794, even writing a song in memory of Rauzzini's dog, Turk.

There is also evidence that his stay and a performance of Messiah in the abbey – with Rauzzini on keyboard – influenced him in composing his masterpiece, The Creation.

Thornton said: "The thought of Haydn conducting Messiah in the abbey and then, as a result, going away in his carriage and starting to think about Creation – well, it's quite overwhelming really."

Bath Philharmonia, which gets no public subsidy and continues largely thanks to the generosity of a single benefactor, is one of the youngest UK orchestras, becoming a professional operation in 2000. That it exists at all is all down to Thornton and a drunken bet.

"A conducting friend of mine bet me a pound that I could conduct all of Mahler's symphonies before I was 30. I bet him that I couldn't."

Thornton then set about losing the bet and to do that, he had to create an orchestra. "My one claim to fame is that I'm the world's youngest conductor to conduct all of Mahler's symphonies. It also means I get asked to do a lot of Mahler."

On Thursday there will be no Mahler. Instead one of the world's two male sopranos, a Moldovan singer called Radu Marian, will make his UK debut performing with Bath Phil in Bath Abbey. Marian's remarkable voice is – perhaps like Rauzzini's – down to nature, an endocrinological condition. One of the songs, The Rose, was by Rauzzini himself, and has not been performed for more than 200 years.

Thornton believes it is time for Bath to celebrate Rauzzini properly, not least with a blue plaque on his Gay Street house. "He is the most important modern musician ever to live in Bath. In the arts, Rauzzini was crucial for Bath and what he created is replicated today."